"Medically it's not physically or logically possible, it's all from the grace of God," said Herald, who is still undecided about a fourth pregnancy.

"Yeah, we're done," she said. "But we have other days when we're not ready to call it quits yet."

Together, Herald and her husband Wil Herald are raising Kateri, 3, Makaya, 2, and Malachi, who is only 7 months old. The oldest and youngest have OI, but the middle daughter is average height and now stands a foot taller than her mother.

Malachi was delivered by Caesarian section in November and was only 5 inches long, weighing in at only 2 pounds, 10 ounces.

He was just released from the hospital in April after getting a virus that overpowered his delicate respiratory system and having hernia surgery.

Though Herald's decision to bear children flies in the face of medical recommendations, she said, "I think it's great and it's something to be proud about."

The hallmark of osteogenesis imperfecta is bones that break easily, but it is also characterized by fragile connective tissue, skin and blood vessels, making all the body's organs more vulnerable, according to the Osteogenesis Imperfecta Foundation.

The genetic disorder is caused by a mutation in one of the genes for collagen, the most common protein in the body, responsible for lung strength. Those with the most serious form often have respiratory problems and are at high risk for asthma.

Doctors can treat the bone density with bisphosphonates and sometime insert rods to lengthen and straighten deformed limbs.

Out of roughly eight different types of the disorder, Herald has Type 3, the severest form other than Type 2, which is fatal, usually at birth.

About half of all patients have a moderate form of the disorder and are taller in stature. Those with Type 3 are usually under 3-feet tall.

"A lot of them are born with a dozen fractures at the very beginning, so a diaper change or a blood pressure cuff can break bones," he said. "It doesn't take a lot to do something to cause a fracture."

Normal Fetus in Malformed Pelvis Could Cause Birth Defects

Because bones are busy repairing breaks, they do not grow properly and are often malformed. Those with OI can expect a normal life span.

Doctors can help manage pain, add to bone density and even straighten limbs surgically with rods. But a pregnancy, especially with a normal-sized fetus, can have "disastrous consequences," according to Tinkle.

"You have someone that small with a two-foot trunk and you put a 20-inch full-term infant into her belly -- already the pelvis is putting pressure on the lungs," said Tinkle. "And it's not just the baby, it's all the fluid and increase in size compression upwards that means [the mother] is going to have problems breathing."

"We don't like to see someone with Type 3 get pregnant because of the risks," he said. "If the mom can't breathe, she's probably going to be OK, but you could have a baby with all kinds of birth defects like cerebral palsy."

Doctors like Tinkle issue "strong recommendations" against getting pregnant because of other risks like damage to the spine and paralysis.

"When you are sitting there is a lot of stress on the spine and we do see what looks like old-age osteoporosis with the spine collapsing down," he said. "It's a constant worry."

Herald said she suffered no physical problems, even though doctors had told her it was impossible to have children.

All three of the Herald babies were born premature, at 32 and 33 weeks.

"Makaya was 4 pounds, 7 ounces and she was double the size of both the other kids together," she said.

The couple relied on the book "Supernatural Childbirth" by Jackie Mize, a Christian guide for women who have been told they could never have children.

Raising three children, especially a 2-year-old who is taller, has not been easy, but she has help.

Wil Herald does the night feeding and she breast feeds Malachi during the day. Herald has a special platform to change diapers and bathe him from her wheelchair seat.

Although her husband disciplines Makaya, Herald said, "It's not really that unusual for me. I helped raise my two nieces who were bigger than me."

Now, Makaya helps her mother change diapers.

As for the medical bills, the couple owns a small business for used baby items, "Katari's Korner," named for their older daughter. They have health insurance.

"We do it part-time," she said. "It's hard to have a full-time anything when you have three kids," she said. "Wil and I are very independent. We don't ask for a lot of help."

Financially, Herald said, "We make it. God blessed us where we're in a position now where we can do that."

Christian Couple Believes in Miracles

Herald said she and her husband, who is training to be a pastor, each experienced their own "miracle."

"He fell off the back of a truck and wasn't supposed to live," she said. "Doctors told my mom I wouldn't make it."

As for ignoring the doctors' advice, Herald said one of the first lessons the couple learned as her husband was taking correspondence Bible classes was about "faith."

"The more we read and the more we studied, we relied on that," she said. "We both wanted children and we believed in God, and he believed in us."

Other experts say they would never interfere with a woman's decision to have a child, despite the risks.

"We believe it's a personal decision," said Mary Beth Huber, director of programs for the Osteogenesis Imperfecta Foundation. "Many women who have bone deformity to the pelvis can carry a child and give birth."

The disability rights movement has empowered women who "a generation ago" would have never considered having a child, said Huber.

"Those with similar forms to Stacey might not have married or felt they didn't wish to have children or were afraid to have children," she said. "We know the risk of a Caesarian section delivery and respiratory problems are greater for mom and her baby, but we also know they can often be managed."

Despite his medical recommendations, even Dr. Tinkle is amazed by Herald's success so far.

"She feels like she can and will continue to do this," he said. "The medical advice is the odds are not a good outcome. But she has beaten the odds."

With the official verification from the Guinness World Records that she is the "smallest mother in the world," Herald said her story gives hope to other women who were told they could not have children.

"My children are my prizes," she said.

"I would tell those women, don't put limits on yourself, don't let people put limits on you, and for the grace of God, don't let anything stop you."